1. Field of the Invention
The present invention relates to printed circuit board structures that include internal copper structures.
2. Background of the Related Art
A typical printed circuit board includes insulating layers and conducting layers that are laminated together using an epoxy resin prepreg. The insulating layers are made with dielectric materials such as polytetrafluoroethylene, composite epoxy materials, or fiberglass-reinforced epoxy laminate. The conducting layers are made of conductive metals, such as a thin copper foil. A prepreg is a material having pre-impregnated composite fibers, such as a woven or unidirectional glass fiber mat that is already impregnated with an epoxy resin.
The printed circuit board provides mechanical support for electronic components and provides electrically conductive pathways between those electronic components. These pathways may include traces formed on the surface of the printed circuit board or in any of the conducting layers. Some of the conducting layers may form other structures, such as a power plane or ground plane that supports the supply of electrical power to the electronic components on the board. Still further, the printed circuit board may include plated through holes that carry power or signals between the layers or surfaces of the board. A plated through hole (PTH) is formed by drilling a hole in the printed circuit board and then plating the walls of the hole with copper.
The glass fibers that extend through the printed circuit board provide strength and dimensional stability to the board. For example, it may be important to prevent thermal expansion of a printed circuit board as its temperature increases so that the electrical connections between electronic components are not affected.